Production of alpha olefins



fatented Sept. 23, 195i PRODUCTION AIiPHA OLEFINS George M. Good,Albany, and Bernard S. Greensfelder, Oakland, Calif., assignors to ShellBevel-i opment Company, San Francisco, Calif., a cor,-

poration of Delaware No Drawing. Application October 17, 1949, SerialNo. 121,908

4 Claims. (Cl. 260-683) which substantially pure alpha olefins may beseparated in large quantities for such synthesis.

Alpha olefins, and especially those having from '6 to about 13 carbonatoms, are particularly suitable starting materials for the synthesis of'a variety of important chemicals and are in de mand. These olefins are,however, usually found in catalytically cracked gasoline and otherpetroleum products only in relatively minor concentrations inassociation with larger amounts of secondary olefins, tertiary olefins,saturates, and aromatic hydrocarbons, and the separation of alphaolefins in suitable concentrations from such mixtures is usually far toocostly and. complicated to be practicable. Thermal methodsfor theproduction of fractions rich in alpha 'olefins from special, costly feedstocks are known and are used, but in these processes the production ofthe desired alpha olefins is accompanied by the formation of largeamounts of byproducts, chiefly gas which is suitable only as fuel-gas.The alpha olefins produced by these methods are therefore costly.

By the process of this invention, such alpha olefins are produced by acatalytic method at a much faster rate and with considerably lessformation of low-valued gas. Some lay-products are also formed in theprocess of the present in- .vention, but these. by-products consistlargely f parafiin hydrocarbons which have considerable value and may beeasily separated.

In the catalytic cracking of hydrocarbons as carried out at present, thematerial to be cracked is contacted with one of the few practicalcracking catalysts under suitable conditions. The product consists of amixture of hydrocarbon types in which alpha olefins are present only invery .small concentrations and from which the isolation of afractionconsisting predominantly of alpha olefins would be highly infeasible. Itis generally recognized .thatthe superiority of catalytic cracking overthe older thermal cracking .methods lies in the fact that the gasolinesproduced, in catalytic cracking operations are richinaromatic-hydrocarbons, secondary olefins and tertiary olefins, whichmaterials lend better antig knock properties to the gasolines. There areliterally thousands of materials and combinations of materials whichare/known to possess a certain ability to catalyze the cracking ofhydrocarbons. However, there are only avery few of these knownmaterialswhich are sufficiently active to warrant consideration forpractical application. The best of the knowncatjalysts for conventionalcatalytic cracking are certain specific activated clays, speciallyprepared synthetic composites of silica and alumina; and speciallyprepared composites of silica and magnesia. Among the materials known topossess a certain ability to catalyze the cracking of hydrocarbons isactivated carbon. Although this material has been often suggested as acracking catalyst, it is well known that it is quite inferior inrespect-of gasoline quality as produced therewith to the mentionedcracking catalysts usedin industry and, as far as we are aware, ithasnever been used commercially. In studying the reasons for this notedinferiority of activated carbon, we found that activated carbon isunique, compared to the other various cracking catalysts, in that withit the catalytic cracking takes place through an entirely differentreaction mechanism. Further study of this behaviorrevealed that bysuitably choosing the feed stock and the reaction conditions, it'ispossible to produce large, hitherto unexpected yields of alpha olefins."I

Inorder-to obtain a product of catalytic crack ing containing a"suitably high concentrationiof alpha olefins, itis necessary to employan acuivated carbon catalyst." It is recognized/that products containingof the order of 50% olefins have been obtained by low temperature; lowspace velocity cracking with a special calcium silicatecatalyst-magnesium silicate compound; the olefins produced in thismanner are however largely beta olefins. (See U. S. 2,441,962) "As willbe seen, activated carbon under suitable con,- dltions is unique inaffording high concentrations of alpha olefins with only relativelyminor amounts of secondary olefins.

i It is not only necessary in the process of" the present inventionto-usean-- activated'--carbon catalyst, but it is also necessary thattheacti vated carbon besubstantially devoid of "so 'called yticvpromoters-i. e., materialswhich im prove the activityofthecatalyst'forspecific re actions such as double bond isomeri zation oraromatization. Thus, impregnation oftheacti vated. carbon .withsmallamounts of s'uch' ma terials as BeO, A1203, ClzOs and B203 wasfound to be damaging to the selective cracking activity of the catalyst.In fact, even the small amount of ash constituents usually present inactivated carbon has a slight detrimental eifect and, as will be shown,it is desirable, though not essential in all cases, to first treat theactivated carbon to reduce" the ash content, i. e. de-ash it." This maybe effected by treating the activated carbon with any acid capable ofdissolving out mineral constituents. Examples of such acids are, forex-' ample, hydrochloric acid, sulfuric acid, phosphoric acid, dilutenitric acid, hydrofluoric acid and acetic acid. It is desirable to washthe 'activated carbon after the acid treatment in order to removeadsorbed acid. Although not essential, this washing is desirable, evenwh'en'a vola tile acid such as hydrochloric acid or acetic acid is used,since it avoids corrosion which is not only damaging to the equipmentbut also causes contamination oi the catalyst with the corrosionProducts. Small amounts of alkali metal oxides or carbp iates w en aplied to. the activated carbon ecrease the" cracking activity somewhat,but, on the otherhandftend to increase the selectivity of-Tthecatalystfo'r the desired reaction. Small amounts of alkali metalcarbonates or oxides, e. g. Oil- 5%," may therefore be advantageouslyapplied tofthefactivated carbon, e. g. by impregnation, in subhcaseswhere especially high concentrae tionsofalpha olefins are desired at theexpense oftheiflsomew'hat decreased net production. The ninction"ofTtheIalkali metal carbonate or oxide is'apparently to neutralize somefew centers in the. surface of 'the activated carbon which may Qthefwie.tend to catalyze the cracking through 'thejfher'ej undesiredmechani'sr'n' of conventional datalytiof cracking. All or the alkalimetals are suitable, but we prefer potassium to the other alkaliinetals.'It is'also possible to add traces of alkaline nitrogen'compounds such,for example, as quinoline and its analogs to the feed stock. 'ruesecempunes also have been found to'poison the catalysts used conventionalcatalytic crack- Infother'words, it often advantageous in the presentmethod to'e'mploy an activated caruse has been slightly: allralized by asmall amouhtbf. analkaline material which is readily embbdid n. theactivated'car'bon and remains so embodiedfuiidrf'the crackingconditional The" 'term""activated carbonsometimes loosely used to referto. all forms of carbon and I nure. substances] whicliar'e, more or lessser cbkefcoalcoke, charred lignite, bone char, etc. WhileVveTeferItactivated'carbon, we do not u h m i ann r; n the contr. the termis usedto designate that form of carbon. or c amb r which is sufficientlymicrour es and possesses an extent of inner surface sn'mcienifto exhibitmarired adsorptive properties. Thus, Mantellstates, referring to gasadsorbents, iI'lieiWdifldl/Var I brought into existence, as an articleof commerce, a new product known as activated carbon, It originated. asa means of defense against toxic gases in warfare. It rapidlyibundindustrialapplications, the extent and novelty of which are. notgenerally appreciated. ust'rial Carbon, D. van Nostrand'Company In 94irhapter X, GasAdsorbents. Acti vatedcarbon as more properly considered,is. a ai d-form. iserbon having a ve y arge r time of a particular type.Thus, as out lviaiitell (loc. cit), It has. been including suchmaterials asfpetroleum I 4 suggested many times that the best adsorbersare charcoals with very many pores of very small diameter, because theywill then present the largest surface for condensation. There are,however, other factors besides the extent of surface. Oneof the mostimportant of these is the arrangementof the surfaces. In the trueactivated carbon the carbon'particle are extremely fine and have acrystallographic structure related to that of graphite with the carbonatoms arranged in closely packed parallel layers, with atoms of theindividual layers disposed at the corners of hexagons. In raphite, theatoms of each layer have 'a fixed positiona1 relationship to the carbonatoms of the adjacent layers, whereas in the activated carbon thispositional relationship of the carbon atom in the different parallellayers is lacking. The structure is therefore turbostratic. [See J.Appl. Phy. l3, 6, 364471 (1942).] The individual primary carbonparticles are. relatively fiat, or plate-like; their size (lengthbrbreadth and thickness) may be measured by electron or X-ray diffractionmethods. Such measurements have indicated the particles to be in theorder of 2 0 to 60 A. in length or breadth'and approximately half asthick, The adsorption isotherms are of the Langmuir type. When thespecific surfaces are calculated irom the adsorption isotherms by theBrunaucr- Emmett-Teller method, surfaces of the order of 1000 squaremeters per gram are usually obtained, although true activated carbonwith surfaces, as lotv'as'OQ square meters per gram are possible. Thepores are relatively uniform in sizeand are usually of the order of 20A, diameter.

Activated carbon, as above defined, is, a known commercial materialproduced by known methods from a variety of carbonaceous materials; itis to be pointed out, however, that while almost all carbonaceousmaterials 'ma'yfbe broughtto a porous state by, a suitable carbonizationtreatment, only certain selected materials may be converted into asuitable activated carbon. Thus, such materials as bone char, dropblack, lamp black, carbonablack, coke, petroleum coke, graphite, ligniteand coal'are not suitable. The "best activated carbons are made from'certain vegetable matters such as coconut shells, fruit pits, cohunenut shells, babas'su 'nut. s'hellsflogwood, ebony a d vegetable ivory:

A w l e mi t d out whe cracki o- P duce alpha olei lns accordingto thisinvention, temperatures are applied which, at, sufficient residence timeof theoilin the heated zone and in the absence of the catalyst, Wouldlead to thermal cracking. In order to maintain this, thermal cracking ata negligible minimum, it is essential to use a highly active carbon ofthe type dc? scribed. Other more or less porous carbons such as theusual decolorizing carbons used in sugar refining, oilrefiningandrelated processes are incapable of catalyzing the reaction ata sufficient rate to permit the use of the low residence times requiredto diminish thermal cracking adequately. Also, at the higher residencetimes. required to obtain a sufficient conversion with the lessactivedecolorizing carbons, undesirable, amounts of aromatic hydrocarbons areformed. Aside from such decolorizing carbons, such materials as.carbonized silica-alumina cracking. catalyst, activated petroleum cokesand pelleted carbon were also found to be entirely unsuited. d

;-A suitable activated carbon catalyst isnot only necessary intheprocess of the invention,

but it is also necessary toiproperlychoose the aci weo:

5. material to be cracked. The'iprocess of the invention is preferablyappliedto cracking feed stocks which contain a major percentage ofparaffin hydrocarbons. Naphthenic hydrocarbons and aromatic hydrocarbonsare detrimental and are to be excluded as far as possible. Thus, weprefer to employ a feed stock consisting of at least 90% paraifinhydrocarbons. Theparaffinicity of a hydrocarbon mixture can be expressedin terms of its characterization factor K, which is defined as the ratioof. the ,cube root of the average boiling point in degrees Rankine tothe specific gravity at'60" F. Through the use of known correlations theaverage boilingpoint for heavy materials may be "calculated from theviscosity. The valuesof K range up'to' about 12.8,,pure parafiinicstocks being between 12.5' and 12'.8. [See Science of Petroleum, OxfordUniversity Press 1938, vol. II, pp; 1378-4380 and Ind. Eng. Chem. 27, 1460 (1935).] We prefer to employ stocks having a characterization factorof at least 12.35. 'While we may crack parafiin hydrocarbons as low ashexane, we prefer to crack those having at last carbon atoms. Thus,paraflinic'stocks boiling above gasoline (205 C.) may be advantageouslyused. If the fraction normally contains appreciable concen-: trations ofaromatic hydrocarbons or naphthenic hydrocarbons, these are preferablyfirst removed by any of the known methods. Even better yields of alphaolefins may be obtained from such high molecular weight paraifinicmaterials as waxy distillates, microcrystalline wax, and even hardparafiin wax having at least carbon atoms.

Although it is possible to crack various hydrocarbon materialscatalytically by the conventional methods at temperatures above 550 C.,such temperatures are rarely used in commercial practice. The reason forthis is that at temperatures above about 550 C. there is a greattendency for the feed material to crack thermally, and whencatalytically cracking a feed stock it is generally desired to avoidthermal cracking as much as possible. A particular char-- acteristic ofthermal cracking is the production of large volumes ofmethane, ethyleneand ethane with much smalier'volumes of C3-C4 hydrocar bons. When oilsare catalytically cracked at temperatures of 550 C. or below, thelighter hydrocarbon products are predominantly propane, propylene,butane and butylene. -The -difrferent character of the'light productsreflects the difference in the reaction mechanisms of thermal andconventional catalytic cracking. Activated carbon likewisecatalyzes thecracking of higher paraflins at lowertemperatures of the order of 300 C.to 450 C., but at such temperatures the product contains only 7 minoramounts of oleflns. [See Herbst, Z. Ang. Chem. 39, 194-6 (1926).] In theprocess of the present invention, however, where the specified activatedcarbon catalyst is employed to catalytically crack the describedparamnic feed stocks to produce alpha olefins, it is essential tooperate the process at higher temperatures. Thus, the process should becarried out at a temperature of at least 540 C. and preferably at atemperature between about 550 C. and 640 C. It will be apparent that atthese temperatures a large amount of thermal cracking of parafiinicstocks would be expected, provided that adequate residence time isemployed. Also, it is well known that carbon catalyzes cyclization. toaromatic hydrocarbons at 'these temperatures. "Thus,

when normal octaneis contacted with activated carbon at. alowxispac'eaveioeity (highresidence. time) and at a temperature above500 C; the; product contains more aromaticsth'an. olefins [SeeMoldavskii et al., J. Gen. Chem; (U. S. S. R.) 7, 1840-47 (1937).]However,'in the'processxof this invention these undesired. thermal':andcatalytic reactions are avoided by the applica-" tion of veryhighspacevelocities new residence times)" and a product consisting largely1-01? the desired-alpha tilefin with very' little ifany; aromatics isproduced. Thus, whereas catalyticcracking is normally operated at aliquid hourly space velocity between about 0.5 and 1.5, the liq-'- uidhourly space velocity in the process of the present invention is 'atleast 5 and m y be-as high as 2-00. If lower space velocities are'use'd,

a product containing undesirable amounts-of arcta ed.- ..The. liquid hur y spa e lo i i fined a th vo u es .Qf. f rsftee to be cracked,measured as a liquid, passed in contact with the volume of the catalystin one hour; The effects 'of 'the temperature and the liquid hourlyspace velocity are illustrated in the; examples. At the required spacevelocities the conversion of the feed stock to productsof lower.molecular weight is. atleast 20% and may; be". above,,90%. The liquidcracked products-cone. sists essentially of alpha olefins and parafiins.Due to the lowconcentrations .of beta 'olefins' and aromatics, thealpha, olefins mayv beeasilyseparated in a substantially pure state. .J

The process, when carriedoutas described, is unique ingthat thecatalytic. cracking. may; be carried out for a considerable period oftime before the catalyst becomescontaminated with carbonaceous deposits.Thus, whereas" the catalysts now in commercial useforcatalyticfc'rackingconvert approximately 1 to 10% of the feed tocarbonaceous deposits and, therefore, require continuous or frequentperiodic regeneration, only a trace (in the order of 0.2 %-0.5%) ,offtiie feed is converted to carbonaceous. deposits the present processand the process may be car ried out for several hours to several daysbefore regeneration becomes necessary. When regeneration finally becomesnecessary or is considered desirablefthe catalyst may be returned to itsinitial eifici'ency by treating it with steam at av temperature betweenabout 650 C. and 750C. Attempts to regenerate the spent catalyst byburning with oxygen-containing gases, as done in the conventionalcatalytic cracking processf failed to restore the activity of thecatalystand: also resulted in destroying a part of the catalyst." Thecatalytic crackingaccording'to the present process may be carried outatany pressure from" subatmospheric pressure up to several atmospheres.I Iowever, operation at substantially atmospheric pressure oratsubatmospheric partial pressure of the hydrocarbon feed stock ispreferred. The subatmospheric partial pressure may be obtainedadvantageously by the use of a suitable diluent material which lowersthe partial pressure of oil in'the cracking zone. It is found that theseIec tivity of the catalyst for the production of olefins; may beimproved at the expense of only a'sniall' decrease in the conversion bythe use of a diluent material. Any inert gas may be employedjja adiluent to afford the reduced pressuraflalthough steam is preferredfa'sillustrated in, chm; il The contacting of theparaffin feed with'thespecified activated carbon under the described conditions may becarriedout in any of meson-= 7 ve'ntional manners.- Onesuitable method 118 1%Example I.

A. feedstock consisting of, normal parafiins ranging from about Cat: toabout C30. (molecular weightabout. 36%) was-.catalytically crackedunder. the following conditions:

Temperature; 550C. Pressure Atmospheric Liquid hourly space velocity 32The catalyst used was a commercial adsorptive activated carbon. Thiscarbon had the. followingproperties:

Form. 4-14 mesh granules Density inbulk-.' 0.50 Adsorption'isothermLangmuir-type Surface-area about1500mfl/gr Ash" content 2.1% Averagepore size A. Structure by electron diflractiorr Turbostraticz' SizeofultlmateC particles 24' A. length, 8' A.

thickness Under/these conditions 43.3 %.'of the feed was cracked toproducts boiling below 289 C. Only about 0.4% of the. change wasconverted to. coke and. only about 5.4% was converted. to propane andlighter gases. Thusthe ratio of liquid prodnets to gas was about 7. Theolefin contents of various fractions of. the product were as shown inthe following table:

Olefin, Product Erection, ."G Percenthy; Weight 4274-- n.- a. ---.i i 8274-99 63 99-125..-- so 125-.1s2 2: 152474."; 5 5]. '51 4.7

The. olefins, were largely alpha olefins as shown by the. following.olefin analyses of. representative fractions:

Composition of Qlefins,

Percent by Weight Product Fraction, C

' Second Alpha aw Tertiary The formation of aromatics under. theseconditions. was small, as. shown by the following weight percentages ofthe 74-152 C....fraction of the product:

Benzene 0.2 Toulenezc 1.6 Ethylbenzene 1.8 Xylcnea 3.0

EsampZaH 4 The above described feed stock was catalytically cracked-withthe same catalyst under the same conditions except that the partialpressure. of the oil feed-stock'was reduced to about mm. Hg by theapplication of 6 moles-of steam per mole of hydrocarbon feed. Thisresulted in .de creasing the conversion to about 33%. On the other hand,the olefin content of the product was increased about 5%, and theformation of; carbonaceous. deposits was approximately halved;

' Example 111 After the. ash content of. the above carbon catalyst wasreduced from 2.1 .to. about 0.27% by treatment withhydrochloric. acid,comparable runs on the catalytic cracking of cetane showed an increasein the conversion from 67.9% .to 70.3%. with no significant. changeintheproduct distribution.

Example IV A straight run California. naphtha boiling ice-- tween. 143C. and 204 C. and containing about 16% by weight of aromatics wascatalytically cracked over activated carbon at a temperature of 500 C.and at a liquid hourly spacevelocity of 1. In this casethe liquidproduct contained 45%. aromatics and 16% total olefins. This ex-; ampleillustrates the totally different results obtained when treating a moreconventional type feed under the more conventional lower. space velocityand temperature conditions.

Example 1 V A batch of an activated carbon'oatalyst was used until itwas heavily contaminated with carbonaceous deposits; The activity of thecon taminated catalyst was only 6% of that of the fresh catalyst.

The contaminated catalyst was regenerated by steaming at 680 C.-700' C.until an amount of carbon was removed which corresponded to the amountof contaminants present. The re generated catalyst was foundto have thesame properties as the fresh catalyst and to be somewhat more active. I

When the catalyst was regenerated at higher temperatures in the range of780 C.'-86D' C., it'was found that the bulk density of the catalystincreased and the full activity was not restored. Regeneration of thecatalyst'at temperatures approximately between 650? C. and 750 C.isrecommended. As stated above, attempts to regenerate the catalyst withnitrogen-air mixtures failed; it appears 'that'in this case both thecatalytic carbon and the inactive deposits are burned indiscriminately.

Example VI The, importance of the temperature and space velocityinproducing alpha oleflns is illustrated in the following: 7

When cracking octane at 500 C. anda space velocity of 1.5, the productconsists predominantly of paraffins and aromatics with only minoramounts of olefins, as can be seen from the-following analyses by weightpercentage of representative fractions of the product: V

Product Fraction, C...

Aromatics 5L 6 18. 8 30. 5 28, 'I saturates 77. 3 66.5 '58. 8 60.0Olefins,(total) .-..---,-r,. 1-7.1 14.17- 10.-7 1L3 Oleiins ProductFraction, 0. Alpha,

Secondary Ratio Total, percent When the operation ,is carried out at 640C. and a liquid hourly space velocity of 102, the olefin content reachesa high level; equally important, the ratio of alpha olefins to secondaryolefins also becomes much higher, as seen from the following weightpercentage analyses:

Product Fraction, C. Alphg/ Secondary Ratio Total, percent Quorum Mmoowumason c:

wwwlor- While 550 C. is about the minimum applicable temperature in thecracking of cetane, somewhat lower temperatures may be applied whencracking much heavier stocks, such as waxes. We prefer to operate,however, at temperatures of at least 550 C.

It will be seen from the above that the present process affords a methodfor the production of alpha olefins in sufficiently high concentrationsto make their separation practicable. This desired result is obtainedfirstly by using a particular catalyst which operates through adifferent reaction mechanism than the usual cracking catalysts;secondly, by employing a feed stock which is very highly paraflinic andpreferably also of high molecular weight; thirdly, by employing veryhigh space rates to minimize the undesired more general reaction ofthermal cracking and the catalytic reaction of cyclization to aromaticsand self-hydrogenation of olefins to paraffins; fourthly, by employingtemperatures suiiiciently high to allow the desired space rate to beemployed while at the same time obtaining a reasonable conversion; andfifthly, by employing a special type of carbon which is sufficientlyactive and selective to allow the desired space rate to be applied andto cause the desired reactions to take place at a rate much above thethermal cracking rate of the feed stock at the temperatures employed.

The invention claimed is:

1. A process for the production of alpha olefins which comprisescatalytically cracking a feed stock consisting largely of parafiinshaving at least 6 carbon atoms and having a characterization factor ofat least 12.35, at a temperature of at least 540 C. but notsubstantially in excess of 700 C. and at a liquid hourly space velocityof at least 5 affording a substantial conversion of the stock, thecatalyst being activated carcon of turbostratic structure, thereby toproduce a product consisting predominantly of alpha olefins andparafiins.

2. A process for the production of alpha oleiins which comprisescatalytically cracking a feed stock consisting largely of paraffinshaving at least 6 carbon atoms and having a characterization factor ofat least 12.35, at a temperature of at least 540 C. but notsubstantially in excess of 700 C. and at a liquid hourly space velocityof at least 5 affording a substantial conversion, the catalyst being ade-ashed activated carbon of turbostratic structure, thereby to producea product consisting predominantly of alpha olefins and paraffins.

3. A process for the production of alpha olefins which comprisescatalytically cracking a feed stock consisting largely of parafiinshaving at least 6 carbon atoms and having a characterization factor ofat least 12.35, at a temperature of at least 540 C. but notsubstantially in excess of 700 C. and at a liquid hourly space velocityof at least 5 affording a substantial conversion, the catalyst being analkali impregnated activated carbon of turbostratic structure, therebyto produce a product consisting predominantly of alpha.

olefins and parafiins.

4. A process for the production of alpha olefins which comprisescatalytically cracking a feed stock consisting largely of parafiinshaving at least 6 carbon atoms and having a characterization factor ofat least 12.35, at a temperature of at least 540 C. but notsubstantially in excess of 700 C. and at a liquid hourly space velocityof at least 5 affording a substantial conversion of the stock, and at asubatmospheric partial pressure of oil, the catalyst being activatedcarbon of turbostratic structure, thereby to produce a productconsisting predominantly of alpha olefins and paraflins.

GEORQE M. GOOD. BERNARD S. GREENSFELDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,895,063 Zurcher Jan. 24, 19332,097,989 Schick et a1. Nov. 2, 1937 2,172,228 Van Peski Sept. 5, 19392,428,715 Marisic Oct. '7, 1947 FOREIGN PATENTS Number Country 7 Date35,617 France Mar. 26, 1930 (Addition to No. 635,889) 416,976 GreatBritain Sept. 19, 1934

1. A PROCESS FOR THE PRODUCTION OF ALPHA OLEFINS WHICH COMPRISESCATALYTICALLY CRACKING A FEED STOCK CONSISTING LARGELY OF PARAFFINSHAVING AT LEAST 6 CARBON ATOMS AND HAVING A CHARACTERIZATION FACTOR OFAT LEAST 12.35, AT A TEMPERATURE OF AT LEAST 540* C. BUT NOTSUBSTANTIALLY IN EXCESS OF 700* C. AND AT A LIQUID HOURLY SPACE VELOCITYOF AT LEAST 5 AFFORDING A SUBSTANTIAL CONVERSION OF THE STOCK, THECATALYST BEING ACTIVATED CARBON OF TURBOSTRATIC STRUCTURE, THEREBY TOPRODUCE A PRODUCT CONSISTING PREDOMINANTLY OF ALPHA OLEFINS ANDPARAFFINS.